1. Field of the Invention
The present invention relates to methods and apparatus for testing sealed containers and more particularly to a method and apparatus for testing a sealed container having a test port including a membrane which is pervious to gas but impervious to water.
2. Description of the Prior Art
In the past, there have been various methods to test the seal integrity of different devices which were designed to be hermetically sealed. In one such device, the formation of a hermetic seal in an assembly resulting from the connection or incapsulation of one or more substrates such as cables by one or more dimensionally recoverable covering members such as heat recoverable sleeves is tested by detecting the increase in the air pressure which occurs during heating of the assembly once the hermetic seal has been made. This is done by providing an aperture in the covering member which communicates with a detection device such as a balloon or a manometer and with a space within the assembly in which there is a build up of air pressure. Therefore, the integrity of the hermetic seal may be tested by observing the balloon to insure that it remains inflated from the air pressure.
Another process for testing the hermetic seal between a substrate and the cover member, includes the formation upon heating of a desired hermetic seal between the substrate and the covering member which is tested by using a device which can detect the excess air pressure which, once the hermetic seal has been made, builds up within a space between the covering member and the substrate. The preferred means for doing this is by use of a probe which passes between the covering member and the substrate into the space and which is connected to a pressure sensitive device such as a balloon or manometer. After use, the probe, which is preferrably made from a plastic material such as nylon can be fused or deformed to insure that the hermetic seal remains intact.
However, the aforementioned prior art methods both require the penetration of the sealed device either by use of a probe or by the use of an aperture which must be closed and sealed after the device has been tested for the hermetic seal. Therefore, the seal integrity of the test aperture or test probe is never known unless some type of secondary test performed to establish the integrity of the test aperture or probe. They may thus prove to be destructive tests.
Another prior art device comprises a waterproof sound apparatus which includes a sealed cabinet filter means attached to the cabinet which is permeable to gases and impermeable to liquids, a speaker attached to the cabinet which has a waterproof construction, and a grill covering in front of the speaker. The cabinet filter means is apparently used to allow equalization of pressure between the pressure on the outside of the cabinet and the inside of the cabinet, and to prevent the introduction of water into the inside of the cabinet. This art is silent with respect to any methods and apparatus for testing the seal integrity of the device.
It is further obvious to those skilled in the art that one method of testing the seal integrity of a sealed container would be simply to submerge the device in some type of liquid solution and then check to see if any of the liquid had leaked into the inside of the container. However, with devices which contain expensive electronic components therein, the introduction of liquid to the inside of the container may have destructive effects on the sensitive electronic components and therefore render the test procedure very expensive and inefficient.
The present invention enables the seal integrity of a closed container to be checked without allowing the introduction of any liquid into the inside of the housing and therefore in situations where the container contains, for example, expensive electronic components inside, would enable any leaks to be detected without destroying any of the electronic components therein. Further, since the test port of the device includes a membrane which is pervious to gas but impervious to water, a successful completion of the test procedure also indicates that the area around the test port is sealed as well as the membrane itself being waterproof, and therefore the necessity of any secondary testing is eliminated to determine the integrity of the test port and any doubt with respect to the integrity of the seal around the test port is eliminated.